Most of these tracks are well-designed, and fit right in with the base game's tracks, but I just cannot get over Voltage Cup (the shoddily-drawn icon isn't a good sign).
The cup starts out strong with 2 memorable tracks and an oddly laid-back Prisons stage, but then you get to Blast Processor. This stage is dreadful, it constantly places dash panels and trick spring to encourage you to go at mach fuck all the time, but it also has sharp turns that lead into pits everywhere you go. It does have a few guard rails, but most are in places you don't need them. And you can't slow down to reposition yourself, lest you be bumped by another racer and fall off the track anyway. This one track is so bad it brings down the entire map pack, not just the cup it's in.
Also, Voltage Viper has some serious performance issues. I could rarely get it above 20 FPS, even when playing at 720p.
If you're reading this review in hopes of downloading this pack, go right ahead and enjoy the great stages on offer, but the moment you load into Blast Processor, just turn off the game, don't waste your time trying to navigate this sloppy course.
While the recent v1.1 update I released doesn't have any gameplay tweaks to Grit Mountain yet [maybe for a future update?], you might want to look into it and see if some of the turning instructions were now addressed, as a handful of tweaks in it were based off feedback regarding conveyance [such as Star Drifter Course's downhill U-turn now having an arch and extra ark arrow to make it easier to tell it's an U-turn].